We have noticed that the spi_mpc83xx.c driver is very slow, the gap
between words are huge.
So I started to optimise it and it still sucks.
However, if I poll the SPIE_NF SPIE_NE bits instead it works MUCH
better, like so:
struct mpc83xx_spi_reg *regs = mpc83xx_spi->base;
u32 event=SPIE_NF;
mpc83xx_spi->tx_count -= 1;
word = mpc83xx_spi->get_tx(mpc83xx_spi);
mpc83xx_spi_write_reg(®s->transmit, word);
if (len >= 2) { /* FIFO is 2 words */
mpc83xx_spi->tx_count -= 1;
word = mpc83xx_spi->get_tx(mpc83xx_spi);
mpc83xx_spi_write_reg(®s->transmit, word);
}
clear_need_resched();
do {
if (event & SPIE_NE) {
word = mpc83xx_spi_read_reg(®s->receive);
mpc83xx_spi->rx_count -= 1;
if (mpc83xx_spi->rx)
mpc83xx_spi->get_rx(word, mpc83xx_spi);
if ((event & SPIE_NF) && mpc83xx_spi->tx_count)
{
mpc83xx_spi->tx_count -= 1;
word = mpc83xx_spi->get_tx(mpc83xx_spi);
mpc83xx_spi_write_reg(®s->transmit,
word);
}
} else if (need_resched()){
clear_need_resched();
schedule();
printk("Cond, rx:%d\n", mpc83xx_spi->rx_count);
}
event = mpc83xx_spi_read_reg(®s->event);
} while (mpc83xx_spi->rx_count);
I am not sure what this polling will do to the system though. Is this really
bad to do?
The resched() stuff doesn't seem to work, probably becase I don't know how
to use it properly :(
Jocke
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